It has been known that, among compounds represented by Formula (XI) [hereinafter referred to as compound (VI-a)]:
(wherein R1 represents a hydrogen atom, substituted or unsubstituted alkyl, or alkali metal), a compound wherein, in the above Formula (XI), R1 represents a hydrogen atom or alkali metal, or a closed lactone form of the compound (VI-a) represented by Formula (XII) [hereinafter referred to as compound (VI-b)]:
inhibits HMG-CoA reductase and has an action to decrease serum cholesterol or the like (Non-Patent Document 1).
Several reports have been published regarding a method using microorganisms to form the compound (VI-a) or the compound (VI-b) from a compound represented by Formula (IX) [hereinafter referred to as compound (V-a)]:
(wherein R1 represents a hydrogen atom, substituted or unsubstituted alkyl, or alkali metal), or a closed lactone form of the compound (V-a) represented by Formula (X) [hereinafter referred to as compound (V-b)]:

That is to say, Patent Document 1 describes a method using filamentous fungi, and Patent Documents 2 and 3 describe a method using actinomycetes. However, since such microorganisms extend hypha for their growth, if they are allowed to grow in a fermenter, the viscosity of the culture solution increases. Thus, it leads to lack of oxygen, and the culture solution becomes inhomogeneous, resulting in a decrease in the reaction efficiency. In order to solve the problem regarding such lack of oxygen so as to maintain the culture solution homogeneous, the stirring speed in the fermenter should be increased. However, if the stirring speed is increased, hypha is sheared, and the activity of microorganisms is likely to decrease (Non-Patent Document 2).
As methods for solving such problems, Patent Document 4 describes a method using Bacillus subtilis, and Patent Document 5 describes a method using microorganisms that do not form spores and do not form hypha. However, the two above methods are problematic in that they require a long period of time for culture and/or reaction, and in that the yield of the compound (VI-a) or (VI-b) of interest to the raw material compound (V-a) or (V-b) is low. Accordingly, it is hard to say that these production methods are industrially advantageous.
As a method for solving the aforementioned problems, there is a method of amplifying an enzyme gene that catalyzes a reaction of forming the compound (VI-a) or (VI-b) from the compound (V-a) or (V-b), so as to improve a reaction rate or a yield. The enzyme gene catalyzing the aforementioned reaction has already been obtained from Bacillus subtilis by the present inventors (Patent Document 6). The effect of increasing the activity of forming the aforementioned compound was obtained by introduction of the gene. However, in terms of a production rate or a yield, industrially satisfactory results were not obtained.    [Non-Patent Document 1] The Journal of Antibiotics 29, 1346 (1976)    [Non-Patent Document 2] Hakko Kogaku no Kiso (Basic Fermentation Technology), pp. 169-190, P. F. Stansbury, A. Whitaker, Japan Scientific Societies Press (1988)    [Patent Document 1] Japanese Published Unexamined Patent Application No. 50894/1982    [Patent Document 2] Japanese Published Unexamined Patent Application No. 184670/1995    [Patent Document 3] International Publication WO96/40863 pamphlet    [Patent Document 4] International Publication WO99/07872 pamphlet    [Patent Document 5] International Publication WO00/43533 pamphlet    [Patent Document 6] International Publication WO00/44886 pamphlet